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Biomedical subjects

J Everett

Publications and source records attributed to J Everett.

49 records · Page 3Linked to original sources
PubMedDate not supplied

The effect of graded exercise on cardiac output of the Jarvik-7-70 total artificial heart in humans.

Animal exercise studies have shown a self-regulated change in cardiac output (CO) with the J-7 total artificial heart (TAH). A 49-year-old, 75 kg patient received a J-7-70 TAH as a bridge to transplant. During bicycle exercise, the TAH heart rate, drive pressures, percent systole, and vacuum were unchanged. Cardiac output was measured by analysis of diastolic air exhaust. Mean arterial pressure (MAP) was measured via a radial artery catheter. Daily recordings of hemodynamics were made from TAH day 35 to 56 at rest, cycling with zero resistance, 18 watts resistance, return to zero resistance, and at rest. Values were as follows: baseline MAP, 75.7 +/- 9.7; LCO, 6.4 +/- 0.2; RCO, 6.8 +/- 0.2. For zero watts resistance MAP was 92.2 +/- 7.2*; LCO, 7.1 +/- 0.2*; RCO, 7.8 +/- 0.3*. For eighteen watts resistance MAP was 101.3 +/- 6.2*; LCO, 7.6 +/- 0.3*; RCO, 8.4 +/- 0.4*. For zero watts resistance MAP was 98.5 +/- 4.9*; LCO, 7.2 +/- 0.4*; RCO, 8.0 +/- 0.4*. The postexercise MAP was 86.4 +/- 4.1*; LCO, 6.2 +/- 0.2; RCO, 6.9 +/- 0.2. For all but baseline and postexercise MAPs, the average response was over a 4 minute interval. The starred values were significant compared to baseline p less than 0.05. Exercise resulted in an autoregulated change in TAH CO in man. Increasing the work of exercise produced an increased CO, reflecting changes in venous return. A TAH patient can exercise for more than 30 minutes with an autoregulated CO and no deleterious effects.

Blood Pressure↗
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Shock tactics.

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Diabetes Mellitus, Type 2↗
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[Cognitive inhibition and psychopathology: toward a less simplistic conceptualization].

"Cognitive inhibition" is a concept that has found a firm place in the interpretation of performance by normal subjects on tasks involving adherence to a plan and suppression of incorrect responses to distractors. The presence of "negative priming" is the classical indicator of cognitive inhibition. Negative priming occurs when, in a sequence of stimuli each of which is composed of a target and a distractor, the distractor of the first stimulus becomes the target of the second stimulus: reaction time to the second stimulus is slowed because of the inhibition applied to the distractor of the first stimulus. The concept has been extended to the interpretation of pathological behavior and symptoms. Pathological subjects have been found to show deficient negative priming. Thus, negative ideation in depression as well as intrusive paranoid associations in schizophrenia have been related to a deficit in the capacity to inhibit inappropriate representations. In this paper, we briefly review some of the experimental evidence from normal subjects that has contributed to the acceptance of cognitive inhibition as a key process in the control of normal cognition, as well as more recent evidence that has led to a revision of the concept. Negative priming in normal subjects has been found to be dependent upon characteristics of the experimental situation as perceived by the subject. In particular, priming is observed when the subject anticipates difficulty in determining the response and proceeds with caution. Thus, inhibition is not an automatic "brake" applied to irrelevant material, but rather the product of strategic considerations within the experimental situation. This revision of the cognitive inhibition hypothesis leads to a re-interpretation of the apparently deficient cognitive inhibition seen in depressed or schizophrenic subjects. According to this more recent interpretation, deficient cognitive inhibition in pathological subjects can be seen as a less adaptive strategic adjustment to the task. The pathology seems to touch higher-level executive functions rather than a deficient inhibitory "brake". In depressed subjects, abnormal performance in selective attention tasks could be related to the underlying pathology in two ways: some depressed subjects show a marked lack of energy and a psychomotor slowing: these subjects do not exhibit normal negative priming, probably because of a reduction of cognitive resources. Other depressed subjects show abnormal performance as reflected by negative priming greater than normal: this result could be related to an exaggerated tendency to verify a correct response. Schizophrenic subjects show a lack of negative priming that seems most plausibly to be related to an ineffectual integration of the experimental instructions concerning both speed and accuracy in the response. This re-interpretation of the cognitive deficiency in pathological patients provides a better fit with recent experimental results from normal subjects, and with cognitive deficits measured in pathological subjects.

Association Learning↗
PubMedDate not supplied

[Deficit in suppression of interference in visual information processing by schizophrenic subjects].

Although many studies have indicated information processing deficits in schizophrenic patients, the precise nature and underlying causes of these deficits remain largely uncertain. One prominent hypothesis is that these patients show insufficient attentional inhibition. This deficit to inhibition has been linked to certain cognitive disorders in schizophrenic patients, including attention deficits, as well as to some clinical symptoms, especially those involving delusional thought, hallucinations,and poor contact with reality. The hypothesis of deficient attentional inhibition, although attractive in some ways, is difficult to work with, because it is not easy to directly measure "attentional inhibition". Several studies involving normal subjects have linked attentional inhibition with performance on a task demanding the suppression of distracting information: the presumption is that efficient attentional inhibition will permit rapid responses because the distracting information will be quickly suppressed, allowing undistracted processing of the target information. The present study measures schizophrenic patients' performance on a task demanding suppression of rapidly-presented visual information. An important methodological feature of this study is that performance is measured in terms of "percent correct responses" rather than the reaction time measures typically used in tasks demanding distractor suppression, such as Stroop-like selective attention tasks. Since reaction times are not considered, the results cannot be interpreted in terms of deficient response organization and execution. Schizophrenic (18) and normal (18) subjects underwent trials in which a visual target was the second of two stimuli presented in rapid succession. Interference produced by a non-target significantly impaired perception of the target for schizophrenic patients. This effect persisted longer in the schizophrenic subjects possibly because of deficient attentional inhibition.

Attention↗
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[Schizophrenia and performance on the Wisconsin Card Sorting Test (WCST): deficits and rehabilitation].

In recent years, there has been a sustained interest in the so-called "frontal hypothesis" of schizophrenia: the idea that clinical symptoms and cognitive deficits characteristic of schizophrenia might be explained by defective function of the frontal lobes. Several studies have attempted to test this hypothesis by examining the performance of schizophrenic subjects on the Wisconsin Card Sorting Test (WCST), a neuropsychological evaluation widely believed to reflect the functional capacity of frontal lobes. A typical finding is that schizophrenic patients demonstrate a tendency to perseverate in producing an inappropriate response in spite of negative feedback. This perseverative tendency resembles the perseveration often seen in patients with frontal brain damage. This article proposes a critical examination of the available evidence linking frontal deficits with schizophrenia via the WCST. As we will show, in most of these studies, only a relatively small number of the available measures on the WCST are made, and consequently many interesting cognitive capacities in schizophrenic subjects have not been adequately examined with this test. These "non-classical" measures will be described and critically examined with respect to their pertinence for further work on schizophrenic subjects. Of particular interest are the "failure to maintain set", which measures cognitive instability, "conceptual responses", which can indicate a certain conceptual capacity even in subjects who show perseveration, and "learning to learn", which can demonstrate a capacity to profit from experience on the test. A second objective will be to critically examine the evidence concerning the capacity of schizophrenic patients to improve their performance on the WCST. To the extent that performance on the WCST reflects the functional level of cognitive capacities important for everyday life, any capacity in schizophrenic patients to improve their performance could have important implications for therapeutic intervention and re-education.

Frontal Lobe↗
PubMedDate not supplied

[Attention deficits and schizophrenia. Multidisciplinary approaches and the Stroop's test].

Since McGhie & Chapman's (1961) pioneering work, there have been continual attempts to clarify the link between attentional disturbances observable in schizophrenics and their schizophrenic symptoms. Venables (1964, 1977) claims that this diminution is a consequence of a badly controlled arousal, resulting in an inadequate filtering at the level of sensory input. Although the notion of a faulty sensory filter is simple and intellectually satisfying, this idea rapidly met with articulate opposition. Broadbent himself, in 1971, revised his model to take into account the way in which semantic aspects influence selective attention, and proposed the existence of a second stage of information processing, coming after the sensory filter. It became increasingly clear that progress in understanding selective attention would depend upon more centrally-directed approaches. In 1935, Stroop developed an ingenious way of studying selective attention. In his task, an "automatic", overlearned task (reading short words aloud) is put into conflict with a slightly more difficult task (colour-naming): the subject has to name the colour of the ink in which a word is printed, but the word itself is the name of a different colour. For instance, when the word "blue" is written in red ink, the correct response is "red". Typically, subjects find it difficult to inhibit the reading response, and take significantly more time to name a colour that forms an incompatible word than take to name the colour of a row of letters "x". This increased reaction time for the incompatible condition is attributed to an "interference" caused by the verbal information contained in the double stimulus.(ABSTRACT TRUNCATED AT 250 WORDS)

Attention↗
PubMedDate not supplied

[Schizophrenia and selective attention].

A comparative study of selective attention was made on 22 schizophrenic inpatients, 18 non schizophrenic inpatients and a control of 22 non psychiatric adults. Signs of schizophrenia were quantified through the BPRS (Brief Psychiatric Rating Scale) and selective attention was expressed as the capacity to resist a distracting stimulus dimension in the Stroop word-colour test. The results indicated higher distractibility in schizophrenic patients, and a positive, significative relation was found between this interference and the "activation" cluster.

Adult↗
PubMedDate not supplied

[Neuropsychology of a psycho-organic syndrome caused by idiopathic hypoparathyroidism. Apropos of a case].

A case of organic psychosis secondary to an idiopathic hypoparathyroidism with intracranial calcifications affecting the basal ganglia and the cortico-medullary junction is described. The results of the skull X-ray, cerebral TACO and nuclear magnetic resonance imaging analyses are presented, as well as a battery of neuropsychological tests. In spite of the extensive calcifications found, deficits on the neuropsychological tests were minimal or non-existent; possible explanations of this discrepancy are discussed.

Adult↗
PubMedDate not supplied

[Deficit in selective attention and its evolution in depression].

Selective attention was measured in 34 depressed patients and 34 controls using a computerized version of the Stroop test, that included a manipulation of the stimulus onset asynchrony (SCA) in order to explore the efficacy of cognitive inhibition as a function of depression and of clinical amelioration of degression after therapy. Clinical tests included a measure of psychomotor slowing [Echelle de Ralentissement de Widlöcher (ERD), the Hamilton (Psychiatric Rating Scale for Depression (HAMD), and the Brief Psychiatric Rating Scale (BPRS)]. Selective attention was measured with the Stroop test, which includes four measures: Word, Color, Color-Word, and Color-Word minus Color, or interference. All of these measures were deficient in the depressed patients, particularly Stroop interference. Even when additional time was given to inhibit the Stroop distractor in the SOA condition, depressed subjects still showed significantly inferior performance. After four weeks of anti-depressive treatment, fifteen of the patients were retested, and showed significant improvement on all the Stroop measures, particularly on Stroop interference. The improvement in performance on the attentional measures was comparable in magnitude to that seen on the clinical scales, and suggests that the interference measure can be a sensitive indicator of clinical status in depressed patients.

Adult↗